When Passing Your Clinical Trial Isn't Enough

Side effects ruin Amgen's day in front of the advisory committee.

Living 4.2 months without bone metastases isn't worth a whole lot for patients with prostate cancer, according to a Food and Drug Administration advisory committee. The panel voted 12-1 recommending against approval of Amgen's (Nasdaq: AMGN) Xgeva as a treatment to prevent bone metastasis. The drug is already approved as a treatment to prevent bone breaks once the tumor has moved to the bone.

The lone vote recommending approval came from the patient representative. All the doctors thought the side effects didn't justify the benefit. Bone metastases are painful, but so is osteonecrosis of the jaw, a side effect seen in 5% of patients getting Xgeva.

The panel's vote is only a recommendation, but there's little chance of the FDA going against the outside experts when the vote is this lopsided.

For Amgen to get Xgeva's label expanded to an earlier indication, it will probably have to show that the earlier use extends survival. That would require a fairly long trial, and it might be difficult to run since Amgen isn't trying to get Xgeva to compete with other prostate cancer drugs such as Dendreon's (Nasdaq: DNDN) Provenge or Johnson & Johnson's (NYSE: JNJ) Zytiga. Patients entering a trial would want to take either Xgeva or a placebo and then be able to take other treatments to prolong their survival even more once the metastases formed. And whether they got Xgeva or placebo before the metastases, they'd want to take Xgeva after metastases formed to reduce breaks like it's approved for now. Lots of variables with no guarantee that Amgen could prove that it improved survival.

The fact that the doctors were so quick to dismiss not living with pain for four months is a bit of a bad sign for Exelixis(Nasdaq: EXEL), which is trying to get cabozantinib approved as a pain treatment for prostate cancer patients, but it's not the end of the world. If cabozantinib has a cleaner side effect profile than Xgeva or a more robust efficacy signal, pain reduction might be taken more seriously. Exelixis is also running a separate trial to measure overall survival, so even if the pain indication bombs, the company has another option for gaining approval for treating prostate cancer patients.